Shifting the Emphasis from Product Testing to Process Testing

By William H. Sperber, Ph.D.

To test the process or test the product? This question reminds me of the riddle that has probably been asked for thousands of years—“Which came first, the chicken or the egg?” Thanks to evolutionary biology, we know that the egg came first, by several hundred million years. However, the answer to the “test the process or test the product” question might never be so clear. I think today we must answer, “Both.” There are times when it will be better to test the process, and other times when it will be better to test the product.

It could also be necessary to test both, or neither. In the modern food industry, product testing preceded process testing as a means to evaluate or assure food safety. For that reason, there remains today an undue reliance, even insistence, upon product testing. This article will discuss testing processed food products, raw foods and uncooked, ready-to-eat (RTE) food products as well as the process, and shifting the emphasis from product to process testing.

Testing Processed Food Products
In the 1960s, the National Academy of Sciences (NAS) and the International Commission on Microbiological Specifications for Foods (ICMSF) attempted to establish procedures for food safety evaluation by organizing and publishing a wide array of microbiological criteria based upon product testing. I will mention just two of the original reports here. They are the following:

These publications include hazard and risk categories, microbiological specifications and product sampling plans. This is where n = 13, 15, 30 or 60 originated. It must be pointed out that these procedures were developed for the analysis of materials of unknown origin and unknown means of control—for example, for materials that could have been procured at any point in the global supply chain—or they were used to evaluate acute problems such as Salmonella in dried eggs in the 1960s, just as today we might evaluate an acute problem of Salmonella in nut products. In the absence of information about the process, product testing is the only means to evaluate food safety, even though we know it doesn’t work very well.

Product testing for food safety is unnecessary today when processed foods are of known origin and produced under known means of control. The major advance in this area was the introduction of the Hazard Analysis and Critical Control Points (HACCP) system of food safety management in the 1970s, with the later recognition and accepted use of prerequisite programs. HACCP is a preventative system designed to control significant identified hazards by means of validated process control measures. It does not depend on product testing to assure food safety. In fact, HACCP was developed precisely because product testing cannot reliably detect low-level defects, such as low-incidence pathogen contamination in foods.

The application of HACCP is best epitomized by the canned food regulations that were developed in 1973. Based upon HACCP, finished-product testing of canned foods is not required and not necessary when the requirements of these regulations are met.[3] A similar food-processing application preceded HACCP and the canned foods regulations by 50 years—the first publication of the pasteurized milk ordinance (PMO) in 1923. Scientists and regulators back then learned that the safety of dairy products could be assured simply by heating them to a prescribed temperature and holding for a prescribed period of time. Pathogen testing in pasteurized dairy products is not required or necessary. However, the PMO does require indicator microorganism testing—coliform and aerobic plate counts—to verify pasteurization effectiveness and sanitary handling post-pasteurization.[4] In many current applications of HACCP and prerequisite programs, product testing for indicator microorganisms (rather than pathogenic microorganisms) may also be performed to verify process control.

Testing Raw Foods or Uncooked Food Products
The success of HACCP and prerequisite programs in assuring the safety of processed foods has lead to increasing political and public pressure for more testing of foods earlier in the supply chain, particularly those that are distributed raw, fresh or unprocessed to the retail and consumer levels—foods such as raw ground beef and fresh produce. Moreover, a number of recent and anticipated food safety regulations have fueled the expectation that raw and fresh foods can be rendered pathogen-free. I will point out two recent examples:

• The E. coli O157:H7 in raw ground beef adulterant rule, published by the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) in 1994.

• The Pathogen Reduction: HACCP rule, commonly called the “MegaRule,” for raw meat and poultry products, published by FSIS. This rule includes Salmonella performance standards.[5] Contrary to the praise heaped on this rule recently, it has nothing to do with HACCP and precious little to do with food safety.[6]

Testing raw or fresh foods for pathogens such as Salmonella or E. coli O157:H7 is often futile because contamination, should it occur, typically occurs at a low level and incidence. Testing foods such as raw ground beef and fresh produce is impractical and inefficient and does not enable effective decision-making. Adulterant rules and pathogen performance standards contribute greatly to this inefficiency and ineffectiveness.

Let’s do a thought exercise. Assume that over a period of weeks or months, your company produces 1,000 twenty-ton truckloads of raw ground beef or fresh produce. Further assume that to meet regulatory and/or customer requirements, you must perform pathogen testing on 15, 30 or 60 samples taken from each truck. After sampling 1,000 trucks, you would have tested a total of 15,000 to 60,000 samples, at great expense. Assume you find 10 trucks that tested positive for the target pathogen, while the remaining 990 trucks tested negative. Ten out of 1,000 trucks is an incidence of 1%. We know in practice that the incidence of pathogens in the few lots of food that are in fact contaminated is usually less than 1%, more like 0.1%—which would be one truckload in a thousand—or even less.

The question that all stakeholders in the food supply chain should find the courage to ask and honestly answer is the following: “What should be done with the 10 trucks that tested positive?” Do you think that these 10 trucks are any different from the 990 trucks that yielded negative results? Quite likely, they are not different. I think we can justifiably assume that any 20-ton truck of raw food will have some extremely low level of incidental pathogen contamination. FSIS itself conceded this point in its 2000 E. coli O157:H7 risk assessment. If you test enough truckloads, you will occasionally find a positive pathogen-test result. Why should a positive truck be flagged for special handling, including destruction? Why are we testing such trucks in the first place?

Pointless testing of this nature costs the affected industries many millions of dollars each year. This is an extremely poor use of resources. We must do better. I am not saying that we should ignore the infrequent public health issues that may exist with certain raw or fresh foods. However, rather than more product testing, I think we need a major collaborative effort among the industry, public health, regulatory and other sectors to systematically expand our food safety focus to all parts of the global supply chain, from farm to table, and to implement HACCP and prerequisite programs where possible. Critical control points can usually be applied only in the processing and consumption links of the supply chain, while prerequisite programs can be applied at all or most of the links. Even if we can accomplish this, the bottom line remains the same. We must acknowledge that, despite our best efforts to implement HACCP and prerequisite programs throughout the supply chain, raw foods will never be 100% pathogen-free and will never be 100% correctly handled and prepared at the consumer level.

Testing the Process
The majority of processed foods now produced in developed countries are produced under known, controlled conditions that are established in HACCP plans and prerequisite programs. Under these conditions, product testing for pathogens can be replaced by process testing. “Testing the process” must be considered from two perspectives. The first would be testing finished products for indicator microorganisms that could be used to verify the effectiveness of process controls, as is done in the PMO.

The second perspective is the sampling of the food-processing environment to evaluate or verify sanitary operating conditions. The production area can be divided into zones that include product-contact surfaces, non-product-contact surfaces, floors and drains and employee and utility areas. Product-contact surface sampling is the most direct way to “test the process” and its potential impact on product contamination. Environmental monitoring can be performed for specific pathogens and/or for indicator microorganisms. Testing for Listeria is often done in wet production areas for refrigerated, perishable, RTE meat and dairy products. Testing for Salmonella is typically done in dry operations that produce items such as dried dairy products, dried eggs, confectionary products and peanut butter and other nut products.

Another kind of environmental monitoring can be very useful as an early warning signal of potential contamination, but it may be overlooked today. In a recent conversation I had with Dr. John Silliker, he reminded me of an important lesson he learned during his career in the evaluation of pathogen contamination in food-processing environments. Rather than relying solely on random microbiological monitoring of particular sites or pieces of equipment, he found it helpful to test environmental samples that were highly representative of the finished product, except that they had received much greater environmental exposure than the finished product. His examples included food materials such as sifter tailings, product spillage in packaging areas, chocolate salvage or rework and peanut butter that accumulated on the scraper blade of a conveyor belt. Detection of a pathogen in such a sample indicated that the production area might be contaminated with the same pathogen and that an immediate investigation should be conducted. It is important that the size of the environmental sample be the same as the sample taken for finished product testing. Like many of you, I know this is a good idea because decades ago, we used a similar procedure, testing the dust collectors in Pillsbury bakery mix facilities. Even today, Cargill and many other millers use an environmental monitoring plan to verify the sanitary quality of milled cereal grains.[7]

Shifting the Emphasis from Product to Process Testing
In summary, while the circumstances vary as described previously, it is sometimes necessary to test the product and sometimes necessary to test the process. The current balance seems to be heavily in favor of product testing, a balance that will become more lopsided as expectations for pathogen-free raw or fresh foods continue to mount.

To more effectively assure the safety of all foods, I believe that we must spend more effort on validating and implementing process controls and process testing measures while eliminating unnecessary product testing. In our post-retirement careers, Dr. Silliker and I hope to stimulate research along these lines to enhance the safety of foods that are sometimes problematic. Now we are trying to organize a collaborative effort to increase the safety of fresh produce by developing microbiological testing methodologies that involve testing produce processes, not the products. If this effort is successful, such an approach could be applied to additional raw or RTE foods, enabling the producers of these foods to use their resources more efficiently while actually improving the microbiological safety of the foods. Insofar as possible, our goal should be to establish microbiological monitoring procedures that enable us to better ensure food safety by testing the process rather than testing the product.

William H. Sperber, Ph.D., has led microbiology and food safety programs in international corporations for more than 40 years. He is Global Ambassador for Food Protection at Cargill, Inc., Minnetonka, MN.

References1. Foster, E. M. 1971. The control of salmonellae in processed foods. A classification system and sampling plan. Journal of the Association of Official Analytical Chemists 54:259–266.2. International Commission on Microbiological Specifications for Foods (ICMSF). 1974. Microorganisms in foods 2: Sampling for microbiological analysis: Principles and specific application. Toronto: University of Toronto Press.3. Code of Federal Regulations. 2002. Title 21; part 113, Thermally processed low-acid foods packaged in hermetically sealed containers; and part 114, Acidified foods. Washington, DC: U.S. Government Printing Office.4. Food and Drug Administration. 2005. Grade “A” pasteurized milk ordinance. Pub. No. 229. Washington, DC: U.S. Department of Health and Human Services. www.cfsan.fda.gov/~ear/pmo05toc.html. Viewed May 1, 2009.5. Code of Federal Regulations. 1996. Title 9; part 304. Pathogen reduction; Hazard analysis and critical control point systems; Final Rule. Washington, DC: U.S. Government Printing Office.6. Sperber, W. H. 2005. HACCP and transparency. Food Control 16:505–509.7. Sperber, W. H. and North American Millers’ Association (NAMA). 2007. Role of microbiological guidelines in the production and commercial use of milled cereal grains: A practical approach for the 21st century. Journal of Food Protection 70:1041–1053.

This article is based upon a presentation at The Consumer Goods Forum, Feb. 4, 2010, entitled “Getting the Most out of Micro Testing…Test the Process or Test the Product?”